In an image forming apparatus in the related art in which toner is supplied by mounting a toner cartridge to a developing device, a shutter which is provided at a toner discharge port is opened by being in contact with a member in the vicinity of a toner supply port of the image forming apparatus when inserting the toner cartridge, and is fixed by a hook being locked. In addition, there is a mechanism in which the shutter is closed by releasing the hook which locks the shutter, when dismounting the toner cartridge. In such a mechanism, a margin is provided in the dimensions, since it is necessary to reliably lock the shutter with a hook for closing the shutter when inserting the toner cartridge. For this reason, the shutter has a structure in which the shutter stops after slightly passing through the position at which the hook locks the shutter.
However, the margin generates a gap between the shutter in the toner discharge port of the toner cartridge and the member in the vicinity of the toner supply port of the image forming apparatus which come into contact with each other when inserting the toner cartridge, when the toner cartridge is taken out. As a result, the toner discharge port of the toner cartridge passes the gap while the shutter is closing, accordingly, the toner leaks.